Circuit interrupter



Aug. .19, 1941. B. P. BAKER CIRCUIT INTERRUPTER Filed Sept. 21, '1938 5 Sheets-Sheet l ZEZ Filed Sept. 21, 1938 5 SheetS-Sheet 2 WITNES SES:

ATTOR mam Au 19, 1941. B p AKER 2,253,oo9

CIRCUIT VINTERRUPTE? Filed Sept. 21, 1938 5 Sheets-Sheet 5 5 r y WITNESSES: INVENTOR Aug. 19, 1941;

B. P. BAKER iNTERRUPTER I 5 Sheets-Sheet 4 n s t' ?1, 1958 ATTORN EY B. P. BAKER I CIRCUIT INTERRUPTER Aug. 19, 1941.

Filed Sept. 21, 1938 5 sheets-sheet 5 NVENTOR ,fi 7 'am/;7 & id/69.

BY y ATTORNE Patented Aug. 19, 1 941 CIRCUIT INTERRUPTER Benjamin P. Baker, T'urtle Greek, Pa., assignor to Westinghouse Electric & Manufactu'ing Company, East Pittsb of Pemsylvania urgh, Pa., a Corporation Application September 21, 1938, Serial No. 230346 23 Ciaims. '(Cl. zoo-150) This invention relates to 'circuit interrupters and, more particularly, to hig'h power circuit breakers of the liqud immersed type. In general, control or the arc after it is drawn is the chef consideration in bringing about 'effective arc extincton in circuit breakers-of all types.

. In liquid immersed int'errupters, the element which is of prime importance in obtaining arc control involves securing relative motion be= tvveen the arc and the arc extingushing liqud. This relative motion may be obtained either by moving the arc through a quantity of liquici or by holding the ar'c stationary and moving the liquid with respect to the are. In the latter method, there are two general directions o"- moving the liquid relative to the arc stream. Per haps the most apparent is a crosschiast Where the lqu'd is moved in a direction perpemlicular to the are and an attempt is made to break the continuty of the are stream by inserting a sheet which forms the hass of the present invention. e

More specifically, when the moton oi arc extnguishing liquid is parale to the are, there is little tehdency for the moving liquid to :inter fere with the flow oi current other than at zero, thus keeping the are energy and gas generation to a minimum value. The iongituclinai flow of arc extinguishing liquid also rapidly removes the excess gas from around the are as it is generated so that as the current approaches' its zero value, the last smalllament of arc may 'oe regarded` as passing through a small hole or chimney in the arcextinguishing liquid. Since the liquid is under considerable pressure and adequate means are provided for the small amount of generate gas to escape freely, it may be assumed that the vwall of liquid surrounding the gas moves toward the arc as the gas bubble contracts with the decrease in current in the cyclic 'variation 'When the diameter of the hole through the arc extingu'shing' liquid becomes small, especially near the current zero, the process of deionization by difiuson to the surrounding cooled liqud is greatly accelerated.

Soon after the'current reaches .its zero value and before the generated voltage can shift from l the circut reactance to the arc tennnals, the

suhjeeted to a io ionzation in the remaining gas is reduced to a very small value. Since the re-ignton or breakdown voltage throug varie's inversely with degree of ionizatioh in the gas and. directy With the absolute pressure on the gas, it is evielet that a large number of vol ts perinch of ar length maybe nterrupted without danger of b eaking the contiruty of the are path just p.. ding the normal current zero. This insures COlSSC-flt arc extinction and avoids the rapid increase in ar'c Voltage which causes a premature current zero and a resulting voltage surge. v

The main object of my invention is .the provislon of an improved ercuithreaker structure wherein circuit inter'uption 'is accomplished in accorclance With aforenaned principies.

Another object of my invention is the provsion a circuit brealrer capable of interrupting large number of volte per inch of contact separaton withoutgenerating appreciable arc energy and with a minimum of are extnguish- .ing liquid deterioraton. v

A fur-ther object of my invention is the provision of a crcuit nterruoter, the performance of whel ally consistent over the entire our garless of power factor or typ interrupted.

i\ rof my inveht on ;is the provs akse emhoomng a cir cuit interr' Wherem the estabc a 'fixed position and animal of are sittindestroying the continuity oi the are h and; the are is main taineo at a reiat i ev? pressure during the major portion of the period; after which the pressure on the stream is materlaily inlished is meinte gulshing creased.

Other objects and advantages relate to details of the interrupter structure and the arraugement of the various parte thereo, all of which will appear more fully 'in the following description when taken in connection with the accompanying drawings, in which Figures 'i and 2 side elevation views partially in section which jointly show the circuit nterrupter of my inventlon, the upper section being shown in Fiat and the lower section in Fi 2.

- Fig. 3 is a; longitudinal sectional viewof the interrupting assenbly of my breaker in the closed'circuit position. c

this last thread of gas Fig. 4 is a longitudinal sectional view of the interrupting assembly in the open circuit position. i

Fig. 5 is a longitudinal sectional view showing the movable contact carrying member of the interrupting assembly on a slightly reduced scale.

Fig. 6 is a fragmentary sectional View showin details of the disconnect contacts between the Operating mechanism" and the movable contact carrying member, and

Figs. 7 to 10 are cross sectional views of the interrupting assembly taken respectively along the lines VII-VII, VIII-VIII, IX-IX, X-X of Fig. 4.

Referri'ng to the drawings, the reference numeral ll designates a fabricated steel support having a base plate |3 which carries the entire circuit breaker structure. The base plate |3 carries a tubular insulator l5 of weather.. proof material, such as porcelain or the like. Concentrically disposed within the insulator |5 is a tubular strain member l1'of insulating materlal having a metallic collar l9 disposed at each end thereof. The lower collar I9 serves as an anchoring means for securing the strain member l1 to the base plate !3. A flange casing member z rests upon the upper end of the insulator !5 and is held in place by means of an annular plate 23 secured by bolts 25 to the upper collar |9 of the strain member l1. The tubular strain member |1 thereby maintains the insulator !5 in position and relieves it of all strain except those which occur in compression. The fiange casing 2| is provided with a cover plate 2150 as to form a complete enclosure or compartment within the tubular strain member l1. This compartment is sealed and adapted to house the current transformer of the interrupter generally indicated at 29. Inasmuch as the specific construction of the current transformer 29 forms no part 'of the invention, it need not be further described.

Mounted upon the cover plate 21 is a metallic casing 3| having a top plate 33 which supports a second tubular insulator 35 also of weatherproof material, such as porcelain or the like. Disposed within the insuiator 35 is a second strain member 31 having metallic collars 39 at each end thereof similar in construction to the collars |9 and the strain member l1. The tubular strain member 31 is secured to the support' plate 33 by means of stud bolts 4| threaded into the collar 39. An annular bearing plate 43 resting on the upper end of the insulator 35 in conjunction with the annular support plate 45 and the bolts 41 serve` to join the upper end of the insulator 35 to the tubular strain member 31. 'I'hus the strain member 31 also maintains the weatherproof insulator 35 in compression and relieves the latter of all other strain. The hearing plate 43 carries a deme-like closure 49'for closing the upper end of the interrupter housing.

The space within the tubular strain member 31 is utilized as an interrupting compartment for housing an interrupting assembly 5l of the circuit breakeri The interrupting assembly 5l, as more clearly shown in Fig. 3, comprises two interrupting elements 53 and 55 disposed in axial alinement and joined by a metallic fiange section 51. The upper end of the interruptng element 53 is provided with a fianged casing member 59 having outwardly projecting support arms 6I. The support arms 6l carry the entire weight of the circuit interrupting assembly and are adapted to be bolted to the annular ring 45 so as to suspend the interrupting assembly 5! with- '1l having a corrugated surface.

in the tubular strain member 31. Thus, the entire circuit interrupting assembly may readily be removed and replaced from the circuit breaker housing for the purpose of inspection, repair or adjustment. The circuit interrupting elements 53 and 55 are constructed of tubular members 63 of insulating material which have metallic collars 65 screw threaded to each end thereof. The metallic collars 65 serve as means in conjunction with suitable bolts, as shown, for joining the two interrupting elements to each other and also for joining the elements to the flange support 59.

Each of the tubular sections 63 carries a plurality of annularly shaped plates or washers 31 and 69 alternately disposed in stacked relation and of insulating material, preferably fiber or other material, which will resist the direct action of an arc thereon. The inside diameter of the washers 61 are smaller than the inside diameters of the washers 69 so as to provide an arc chamber It will be noted that the larger washers 61 of the interruptlng element 55 have an inside diameter which is larger than the inside diameter of the plate 51 in the interrupting element 53. Thus the general diameter of the arc chamber 11 of the interrupting element 55 is larger than that in the interrupting element 53, the purpose of which will appear more fully hereinafter.

Disposed between the flange support 59 and the upper collar 65 of the interrupting element 53 is a fixed contact support 13, in this instance carrying four resilient contact fingers 15. The contact ngers 15 are connected by means of fiexible shunts 11 to the flange support member 59. A second fixed contact support 13 is also disposed between the fiange spacing member 51 and the upper collar 65 of the interrupting element 55. This second fixed contact support also carrie four fiexible contact ngers 15. In the latter instance, however, these Contacts are connected by flexible shunts 19 to a movable contact member which will be explained more fully hereinafter.

The moving contact assembly is carried by a rod-like Operating member generally indicated at BI extending longitudinally through the interrupting elements 53 and 55. The Operating member BI is more clearly shown in Fig. 5 and constitutes a central support member 83 of insulatlng material having a threaded metallic fitting 35 secured to each end thereof. To the lower metallic fittng 85 is screw threaded a metallic cep member 81 which, in turn, supports a contact ring 39 having three main current carrying contacts 9l and an arcing contact 93 formed thereon. Surrounding the support rod 83 is a sleeve of insulating material which is highly arc resistant. surrounding the sleeve 95 and adjacent the .contact ring 89 are a, plurality of washers 91 and 99 alternately disposed and having different outside diameters so as to present a corrugated external cylindrical surface. Adjacent the group of wash ers 91 and 99 at the lower end of the sleeve 95 is a metallic sleeve Hil, the lower end oi' which has a squared recessed portion !03 to which the ende of the flexible shunts 19 are connected. The up per en'd of the conducting sleeve o supports a second contact ring 89 of somewhat smaller diameter than the ring at the lower end of the assembly. The upper contact ring 69 is also provided with three main current carrying contacts 9| and a single arcing contact 93. Disposed about the upper contact ring 89 is a second series o! 'port arms Si.

fiber washers 91 and 99 similar to those previously described, with the exception that washers 91 in this instance have a smaller out-side diameter. Immediately above the second series of washers 91 -and 99 is a metallic guide sleeve I screw threaded to the upper metallic fitting 85 of the support rod 83. Thus the sleeve l05, when screwed into clamping engagement with the upvper 'plate assembly, holds the entire assembly rigidly together as a unit.

It it will be noted that the contacts 9! and 9 i of the upper contact ring 89 are adapted to register with the contact finger 15 on the circuit interrupting element 53 when the interrupter is in the closed circuit position, as shown in Fig. 3. Likewise, the Contacts 9! 'and 93vof the lower conmore clearly shown at "5 in Fig. 1. The actu- 4 partment within the tubular casing IT. The pull tact ring 89 engage the contact fingers 15 of the lower interrupting element 55. Thus, as shown in Fig. 3, an electrical circuit is established from the fiange'd support 59 through the flexible shunts H to the contact finger- 15, the upper contact ring 89, the conducting sleeve loi, the exible shunt 19 to the' contact finger 15 of the interrupting element 555 to the Contacts si and 953 of the lower contact ring 89, and finally to the metallic cap S?. When the circuit interrupting assembly Ei is positioned within the housing, as shown in Fig. 1, external circuit connections from the ange support 5@ are made by means of a exible shunt iii? to a terminal stud !te passing through the side of the dome-shaped cover i&

The cap member ti of the movable Operating member iii is'provicled, as shown more clearly in Fig. 6, with a disconnect contact assernbl'y housed within the collar MU screw threadei thereto. collar iii is provided with a plurality of contact firigers MS adaoted to make 'siicling en gageme'nt with a hayohet type contact ti carrid by the upper enti of an actuatihg iriember 4 tou, lcl' s' terminal s 625 passing throu the The inner rnis of the termirai stucls iii are respectiveiy connecte by suitable leads isi arcl to the current transferta e The operatihg meniher iii arranges !Cka cprccating moi/em it axially o the inter rupting elements s moved dovm wardly to 'the open circuit position by means of battery of compression sprngs &135 disposecl he ttveeh a fixed pressure plate 'and' a movable pressure late 039. The threci pi'essure 'plote &s'i is secured to the upper ends of a ;olurality of guide and support rocls Mi anchored in the sup- 'l he lower and movable pressure plate is securecl to a screw threarled portion i of the guide sleeve sos formihg` the upper end of the Operating member ei and is provided with suitable apertures through which the soo port rools Mi may pass and serve'to guidc 'the plote during its reciprocal movement.,

The operating meniher &i is held in the closed position against the action of the springs i, as shown in Fig. 3, by a suitable actuating mecha- 'nisin connected to the Operating member ill, as

rod !41 is sealed with respect to the' casing by means of a tube ne, the upper end of which is joined in a liquid-tight manner to the coverplate 27, whereas the lower end is joned in a similar manner to the base plate l3. The lower end of the pull rod !41 is coupled to an arm !49, which, in turn, is 'Secured toa torsion shaft |5l having an actuating arm !53 which is adapted to be coupled to a suitable breaker Operating mechanism. The right-hand side of the torsion shaft !55 andthe arm !49 are disposed within a liquid tight chamber !55. From the foregoing description, it is apparent that the Operating mechanism and the interrupting assembly si is submerged in an are extinguishing liquid which is maintained separate and apart from the insulating vliquid contain'ed in the transformer chamber the springs force the Operating member sa clownwardly to the position shown in Fig. 4. The operatirg member 'i ll, however, due to actuation of the actuating mechanlsm MS, as controlled by the mili red M'i, continues its downward movement until the lower end of the actuating member i t'i strikes the stop lol provided on the upper side of the cover plate ai, as shown in Fig. 2. The travel of the Operating memberl ll is greater than that of the cooperating member &I and thue produces a disconnect gar between these members when the interrupter is in the open circu't position. This disconnect takes place between the spring pressed contact fingers ii@ carrieci by the collar iii at the lower emi of the Operating member %i and the bayoret contact 5 carried by the upoer end of the operating member i ll. During the closing movement of the inter rupter, the actuating mechahism m, operated; by the puil reci MTI, raises the member :lil so that the contact ii engae'es the spring pressed con tacts to complete the eiectrical circuit ieetweeh .the Operating member &i and M'i'. A

blight. hufling action is provided to lesson the a relatively high speed. This high speed motion is arrested at the emi of the opening strolse by means of a butter-plote &tii dieioosed in the path of movement of the pressure plote i! and cuided the support rods Mi. The butter plote BG! is resiliently urged towarrls the pressure plate I 39 by smilies 953 encircling the support and guide rods izle.

The operating member M is further guided during its reoiprocating movement at its upper end by the closu'e plate Ist Secured to the upper end of the support fiange 69. In order to prevent binding of the guide sleeve !05 as it passes through the cover plate !66, the guide sleeve !05 is grooved circumferentially, as shown. The operating member a is also guided by' a closure plate !61 secured between the lower collar 66 o! the interrupting element 93 and the flange casing 51. The aperture in the closure plate 161 through which the conducting sleeve IM oi' operatng member 8| is adapted to slide, is provided with an annular recess !69 which has its innermost wall tapering towards the sleeve IOI so as' to provide a knife like scraping edge adjacent the sleeve. This scraping edge maintains the sleeve Illl !ree from foreign matters such as may occur from the establishment of an arc within the arc chamber 1 l during circuit interruption and thus prevents the sleeve n from binding as it passes through the closure plate l61. A similar scraping device is provided in the form of a guide annulus l1| at the lower end of the circuit interrupting element 55 having a scraping edge 113 and which serves to guide the Operating member l|1 and the cap member 61 during reciproc'ating movement and also keeps the bearing surfaces of these latter members free from foreign matter.

As shown more clearly in Figs. '1 to 10, the arc chambers as defined by the washers 61 are of generaily clrcular cross section. noted that the arcing contacts 93 carried by the two contact rings 99 extenda short distance laterally from their respective contact rings. The washers 61 are provided with notched portions !16 to provide an elongated groove or passage into which the arcing contacts 93 are adapted to be moved during the opening movement oi! the interrupter. The washers 91 on the member s have a diameter such that there is but slight clearance between these washers and the washers 61 deflning and limiting the side walls of the arc chambers 1I. The outside diameter of the insulating washers 91 of the upper group is slightly greater than the outside diameter of the guide sleeve lfl I. Thus when the Operating member !I is moved downwardly, arc extinguishing liquid within the upper arc chamber 1! will be displaced upwardly about the arcing contact 93 and longitudinally of the notched portion !15.

'Any tendency of the washers 91 on the member 6| to interlock with the washers 61 forming the arc chambers 1| due to lateral displacement oi' the member 8 I, is avoided by making the washers 91 of slightly greater thickness than the washers 61 as shown. It will, oi' course, be ob vious that the same result is obtained by making the washers 61 of greater thickness than the washers 91. The desired result may also be obtained by using a different spacing between the stationary washers 61 than between the movable washers 91.

It should also be noted that`the guide sleeve !65 is oi' less diameter than the washers 91. Thus when the Operating member &I is moving downwardly, a greater Volume of material, as constituted by the washers 91 and 99, is moved into the arc chamber 1| and out of the space between the arc chamber 1| and the closure plate !65 than is moved into the space by the guide sleeve !95, causing a partia] evacuation of this space. The space above the are chamber 1| in the interrupting element 63 may be designated as an expansion chamber !11 into which arc gases resulting !rom an arc drawn between the arcing contact 99 and its corresponding"xed contact flnger 15 may escape. Flow of arc gases into the It should be' i Fig. 4.

.expansion chamber l11 is also augmented by virtue of the partial evacuationwithin the chamber as above described. i In order to relieve the chambel11 of excess pressure during the latter part oi' the arcing period and also to provide means Ior the in flow of arc extinguishing liquid following arc extinction, a vent opening is provided through the side wall of the tubular member 63, as shown at |19. The vent opening !19 is so proportioned that during the initial opening movement ot the operating member sl, partial evacuation will take place at a rate greater than the in flow of arc extinguishing liquid from the arcing space 1l tending to displace the evacuated space.

In connection with the interrupting element 55, the relative proportion between the diameters of the washers 91, the connecting sleeve u and the cap member 81 are maintained, as in theinterrupting element 53, that is, the washers 91 are of slightly greater diameter than the cap member 91 and the upper end of the Operating member ll1. This arrangement provides a piston for orcing arc extinguishing liquid longitudinally of the notched path !15 of the arc passage 1l. Likewise the external diameter oi the conducting sleeve u is of smaller diameter than the external diameter of the washers 91. Thus the space between the lower arc chamber 1I and the closure member !61 forms a second expansion chamber a which is slightly evacuated during the opening movement of the operating member 6! so as to cause a ready escape of the gas from the arc chamber 1l into the expansion chamber. The expansion chamber l6l is also vented at [83 in the side Wall of the lower interrupting element 55.

The operation oi the interrupter is as follows. Assuming that the Operating member is in the closed circuit position, as shown in Fig. 3, and is released by the actuating mechanism !41, the

accelerating springs !35 will force the Operating member 8l downwardly to the position shown in During the downward movement of the member BI, an arc will be' drawn between each of the arcing Contacts 93 and its respective fixed contact nger 15 of the respective interrupting elements 53 and 55. These arcs will bear a series relation with respect to each other by virtue of the electrical connection between the upper contact ring 89 through the conducting sleeve o and the fiexible shunts 19 to the lower contact ngers 15. These arcs are adapted to be drawn into the notched portions !15 of the respective arc chambers 1| and held against substantial lateral movement by virtue of the stack of`washers 91 which Iollows the arcing contact to fill in the arc chamber. The respective arcs are, therei'ore, conflned to an elongated relatively narrow arc passage which is closed at the lower end and opened only at the upper end into the expansion chambers |11 and I9l. Arc gas, generated as a result of decomposition of arc extinguishng liqud by the arc, will escape freely longitudinally of the arc into the respective expansion chambers. Escape of the gas from around the region oLthe arc is also accelerated by virtue of the evacuating eifect produced by movement of the Operating member Bl. Removal of arc gases is further facilitated by the pumping action produced by the Operating member 8! as it moves downwardly causing the displacement of arc extnguishing liquid longitudinally of the arc in a direction towards the respective expansion chambers. In

this manner, 'the pressurecf arc gas is maintained low' during the initial. stageof arcing, thereby maintaining the arc ene gy *at 'a minimmm Pressure upon the arc stream doesnot reach appreciable proportions until a timejust -priorto arc extinctiom 'The rise' in pressure which produces arc extinction results from an equalization' of 'pressure within the expansion" chambers' and the arc chamber, under which condition the rate oi escape of gas from the arc chamber to the expansion chamber is decreased.

The desired increase in pressure upon the arc during the final stage of arcing is further augmented by a decrease in velocity of the Operating member 8| towards the end of its stroke( As theoperatin'g member' 8l loses velocitydue' to a decrease 'in tension of the sprin'gs |35, the vol'- ume of the 'expansion chambers are increased at a rate which is iess than the rate of increase in volume of gas being generated in' the arc chambers. The 'arcpress'ure is also constantly increased as a result of piston action, by movement of the washers 91 farther into the arc chamber "H, as a result of; an 'increasein resistance to the flow ofiiquid from the arc cham- I ber. It is, therefore, apparent that arc eXtinction takes place without breaking the continuity' of the arc stream; 'I *his' method of arc 'extinction avoids a rapid increase in arc voltage,

sudden peaks of arc energy and the forcing of a current zero with accompanying voltage surges and mechanical shocks. The fact that the arc is confined to a passage of relatively small cross section and a flow of arc extinguishin'g liquid is continuously maintained longitudinally of the arc, the interrupter shows a high degree of consistency over the entire current range regardless of power factor or the type of circuit being interrupted. V Although I have shown and described a specific circuit interrupting' structure, it is to be` understood that the same is :for the purpose of ill'ustration and that changes and modifications may be made' by those skilled in theart without departing from the spirit and scope of the appended ciaims. i i I claim as my invention:

1. In a circut interrupter, a quantity of arc extinguishing liquid, means of insulating material dening an elongated arc passage immersed in said liquid, said arc passage having walls which present irregular surfaces 'and being open only at one end, a pair of "cooperatingv contacts 5 ating with said plungermember for drawing an arc from a point outside said arc chamber into the arc chamber along said constricted arc path,

the products of decomposition of the arc being caused to flow longitudinally of the arc path to wards the open end'ofsaid arc chamber, said plunger member' displacing arcextinguishing liquid within said arc chamber to cause a flow of I liquid longitudinally of the arc towards the open end'of said 'chamberto assist in ex'tinguishing 'the arc. v

.3. In a circuit interrupter, a quantity of arc extinguishing liquid, 'means of' insulating material immersed in said liquid defining an arc chamber open only at one end and the inside walls of which have grooves extending therearound, a

plunger member'of insuiating material having,

grooves extending therearound adapted to be moved intosaid arc chamber, a fixed contact adjacent theopen end of said arc chamber, a

'cooperating contact carried by said plunger member for 'drawing an arc'into said arc chamber, said plunger member substantially filling said arc chamber when moved therein to prevent substantial lateralmovement of the arc from the position occupied when drawn and 'for causing a blast of arc extinguishing liquid long'itudinally of ,the arc toward the open end of said arc chamber. e

4. In a circuit interrupter, a body of arc extinguishing liquid, means of insulat ing material immersed in said liquid d'efim'ng an elongated arc chamber and a cylindrical passage disposed side.

by side and havingicontinuous communication with-each other, a stationary contact disposed outside said arc chamber, a piston movable in said cylindrcal passage,`a cooperating contact carried by said piston and adapted to be moved therewith through said arc chamber into and out of engagement with said stationary contact,

'said arc chamber having a vent opening'` only at at least %one of which .is permanently positioned outsidesaid arc .passage adjacent .the -open end thereof, a movable member of insulating material having irregular suraces and supporting the other of' said pair of contacts, and means volume ofsaid enclosed space and venting means for controlling' the pressure within said enclosed space.

formoving said -memberof insulating material i "into said arc passage to establish an arc thei-ein,

said member of insulating material displacing a portion 'of the arc extinguishing liquid in said.-

passage to providea'flow of arc extinguishi-ng liquid longitudinally of the arc toward the open end of said passage to aid in' extinguishing the arc.

2.-In a .circuit interrupter, a quantity -of-arc rial defining an arc .chamber -immersed in said i liquid. said arc chamber-being open only 'at one end, a grooved' surface plunger member of in-v 6. In a circuit interrupter, means defining an arc chamber, separable contacts for drawing an arc within said arc chamber, means for actuating. said contacts to open and closed positions, means defining 'an enclosed space of variable' volume 'adjacent said arc chamber and into which arc gases are adapted to flow, meansactuated by said contact` actuating means for increasing the volume of .said. enclosed space' 'during theinitiai extinguishing liquid, means of insulating, matesulating material movable into said arc chamber to provide an arc path of constricted cross section between the plunger member and a portion of the wall of said arc chamber, means cooperstage of arcing at a rate greater than the rate of increasein volume of gas being generated in -said arc chamber and means' for'venting said'` enclosed space. 4

7. In acircuit interrupter, means defining an arc chamber, separable contacts for drawing an arc within said arc chamber, means for actuating said contacts toopen and closed positions, means deflning an enclosed space of variable Volume adiacent said arc chamber and into which arc gases are adapted to flow, and means actuat'ed by said contact actuating means for increasing the Volume of said enclosed space during the initia stage of arcing at a rate g'reater than the rate o! increase in Volume of gas being generated in said arc chamber, said last named means causing the Volume oi' said enclosed space to increase during the final stage of arcing at a rate less than the rate of' increase in Volume of gas generated by the arc.

8. In a circuit interrupter, a body of arc ex tinguishing liquid, means defining an arc chamber immersed in said liquid, separable Contacts at least one of which is movable for drawing an arc in said arc'chamber, means defining a ventinmchamber adjacent said arc chamber into which arc gas from said arc chamber is adapted to flow, and an Operating member extending through said arc and venting chambers for actuating said movable contact and causing arc extingulshing liquid to flow longitudinally of the arc in a direction opposite to the direction of contact movement, said Operating member causing a reduction in hydrostatic pressure on the arc' during the initial arcing period to facilitate the flow of gas into the venting chamber anda sudden increase in hydrostatic pressure near the end of the arclng period for raising the reignition voltase.

9. In a circuit interi-unter, a body of arc extinguishing liquid, an enclosure immersed in said liquid, an arc chamber within said enclosure, an expansion chamber within said enclosure adjoining said arc chamber, a 'stationary contact adjacent one end ot said arc chamber, a moving contact adapted to cooperate with said stationary contact. a movable contact carrying member extending through said arc chamber and having a portion normally extending into said expansion chamber, means for actuating said contact carrying member to separate said contacts to establish an arc in said arc chamber and to move the portion of said contact carrying member within said expansion chamber into the arc chamber, the

. portion of said contact carrying member moved into said arc chamber being so proportioned with respect to the arc chamber that the arc is conflned to a narrow elongated path therein and the pressure within the expansion chamber is materiaily reduced upon movement of the contact carrying member therefrom at least 'during the initial stage ot the arc extinguishing. operation, and venting means for controlling the pressure within said expansion chamber.

10. In a circuit interrupter, a body of arc extinsuishing liquid, an enclosure immersed in said liquid, an arc chamber within said enclosure, an expansion chamber within said enclosure ad'- Joining said arm chamber, a stationary contact adjacent one end of said arc chamber, a piston member normally within said expansion chamber and movable into said arc chamber, a movable contact carried by said piston member and adapted to cooperate with said stationary contact, means for moving said piston member into said arc chamber to establish an arc therein and to force arc extinguishing liquid in a direction lonzitudinally ot the are towards said expansion chamber, said piston member upon movement out oi' said expanslon chamber causing a reduction in pressure therein to aid the products o! decomposition of the arc within the arc chamber to now into the expansion chamber to prevent the formation of pressures within the arc chamber during the initial arcing period detrimental to arc extinction, and means for venting said expansion chamber.

11. In a circuit interrupter, a body of arc extinguishing liquid, means within said liquid defining an arc chamber open at one end, an expansion chamber communicating with the open end of said arc chamber and said expansion chamber being otherwise substantially closed except for the vent means set forth below, a plunger member movable from said expansion chamber into said arc chamber, means for simultaneously drawing an'arc within said arc chamber and moving said plunger member into said arc chamber, said plunger member confining the arc to a relatively constricted path longitudinally of said arc chamber and subjected it to a longitudinal flow of liquid, and relatively restricted vent means for said expansion chamber cooperating With the movement of said plunger member out of said expansion chamber to prevent the rise of pressure above a predetermined value within said arc chamber during the initial stage of arcing.

12. In a circuit breaker, an interrupting unit comprising a stationary and a movable part ar- 'anged to form a plu'ality of serially associated interruptng elements, said stationary and said movable parts having alternate sections of conducting and insulating material disposed in endto-end relation, separable contact means arranged to interconnect the conducting sections of said stationary and said movable parts to form a conducting circuit through said unit when said conducting sections are disposed in staggered 'relation, said movable part having at one end of each section of insulating material an enlarged portion acting as a piston, and means for moving said movable part to break the electrical connection between said conducting sections to establish a plurality of serially related arcs and to bring the insulating sections of said moving part to a position opposite the insulating sections respectively of said 'stationary part for drawing and conning each arc in the space between an insulating section of the movable part and an insulating section of the stationary part.

13. In a multiple break circuit interrupter, a body of arc extinguishing iiquid, means within said liquid defining a plurality of arc chambers disposed innalinement, a fixed contact adjacent one end of each of said arc chambers, an operating member movable through said arc chambers, a cooperating movable contact for each fixed contact carried by said Operating member, said Operating member having a piurality of enlarged portions each of which is normally disposed outside of a respective arc chamber when said fixed. and moving contacts are in engagement, and means for actuating said Operating member to establish an arc in each arc chamber and to move said venlarged portions of said operating' member into their corresponding arc chambers, said enlarged portions upon movement into said arc chambers cooperating therewith to conflne said arcs to fixed paths and subject the arcs to a longitudinal flow oi arc extinguishing liquid. i

14. In a multiple break circuit interrupter, a body of arc extinguishing liquid, a tubular casing immersed in said liquid, means dividing said casing into a pluraiity of expansion and arc chambers alternately disposed longitudinally of said casing; an Operating member extendin a 2,253,oo9 i through said chambers and closing one end of' supporting the other of said contacts, and means for moving said movable member into said arc passage to-establish an arc therein and to cause.

a flow of arc-e'xtinguishing liquid longitudinally of the arc to aid in extinguishing' the arc, said -grooves and ridges in said arc passage being so proportioned and arranged with respect to the grooves and ridges on said movable member that operating member and disposed outside its re V spective arc chamber. when said fixed and mov-' able Contacts are in engagement, and means for actuating said operating member to establish an arc in each of said arc chambers and to move said piston from their respective expansion chambers into their arc chambers, said pistons driving a quantity of arc extinguishing liquid from said arc chambers longitudinally of the arcs into said expansion chambers and lowering the pressure within said expansion chambers to assist the products of decomposition of said arcs to escape into said expansion chambers.

15. In a circuit interrupter, an arc chamber, separable contacts for establishing an arc within said chamben a movable member extending through said arc chamber for actuating at least one of said Contacts; and a closure for one end of said arc chamber having an -aperture therein through which said movable member is adapted to slide, said closure having aportion surrounding said aperture whichtapers inwardly with rer spect to said chamber and towards said movable member to provide a scraping edge for remov- 'ing particles of decomposition of the arc from vide a corrugated wall dening said arc passage,

separable Contacts adjacent one end of said arc passage, a movable member including a stack of washers of insulating material for carrying 'at least one of said contacts, alternatewashers comprising said movable member being ot dlfierent e external diameter to provide a corrugated external surface, and means for 'moving said movable member into said arc passage to establish an arc therein and to provide a flow of arc extincomprising said movable member having a thickness different than a plurality of the washers defining said arc passage to prevent interlocking of said movable member with the side walls of said arc passage as the result of lateral thrusts I' 'grooves and ridges therein, a pair o! cooperating contacts, at least' one of which is positioned adjacent one end of said arc passage; a movable member at least partially of insulating material having alternate grooves and ridges thereon and interlocking of said movable member 'with the side walls of said arc passage is prevented.

19.`In a circuit interrupter, a quantity of arcextinguishing liquid, means of insulating'material defln-ing an elongated 'arc passage open only at i one end and immersed in said liquid, a pair of cooperating contacts, at least one of which is positioned adjacent the open end of said arc passage; a movable member at least partially of insulating material supporting the other of said Contacts, and means for moving said movable member and its associated contact into said arc passage to establish an arc therein, said movable member being closely tted with respect to the insulating material for holding the alternate sections of conducting and insulating material of said movable part together, separable contact means arranged to interconnect the conducting sections of 'said stationary and said movable parts to form a conducting circuit through said unit When said conducting sections are disposed in staggered relation, and means for moving said movable part to break the electrical connection between said conducting sections to establish a plurality of serially related arcs and to bring the insulating sections of said moving part to a position opposite the insulating sections of said stationary part for drawing and confining each arc in the *space between two opposed insulating sections.

-21. In a circuit interrupter, an arc chamber, stationary contact means in said arc chamber, a movable contact member coacting with said contact means, said contact member comprising two coaxial separable sections, at least' a portion of both sections being within said arc. chamber when the interrupter is in the closed position, and means Operating said contact member to open circuit position to establish a circuit interrupting arc in said chamber between said contact means and one of' said sections and subsequently separate said sections to establish an isolating break outside said chamber.

22. In a circuit interrupter, an arc chamber, stationary contact means in said arc chamber, a movable contact member coacting with said contact means, said contact' member comprising -two coaxial separablesections operable at least in part through an opening in one end of saidarc chamber, at least a portion' of both sections being within said arc chamber when the interrupter is in the closed position, and means operating said contact member to open circuit position'to establish a circuit interrupting arc in said chamber between said contact means and one of said sections and subsequently separate said sections to estabiish an isolating break outside said chamber, said sepa'able sections coacting with each other and said arc chamber to seal the opening therein during the circuit opening operation of the interrupter.

23. In a circuit breaker, an interrupting unit comprising a stationary and a movable part arranged to form a piurality of seriaily associated interrupting elements, said stationary and said movabie pa'ts having alternate sections ot conducting and insulating material, separabie contact means arranged to interconnect the conducting sections oi said stationary and said mov- 15 able parts to form a conducting circuit through said unit when said conducting sections are disposed in staggered relation, and means for moving said movable part to break the eiectrical connection between said conducting sections to establish a plurality of serially related arcs and to bring the insuiatng sections o! said moving part to a position opposite the insulating sections of said stationary part, said conducting and insula'ting sections being substantiaily of equal lengths so that each arc drawn between said separabie contact means is confined in the space tween two opposed insulating sections.

BENJAMIN P. BAKER. 

